R-889: every disk percent is df's (used / (used + available)); the tile says Rendszer, not Rendszer (/) (09 decision 138)

The box divided used by the whole filesystem, so the 5 % reserved for root made a full disk read ~5 points low
(61.8 of 68.7 GB = 90 % where df said 95 %) and the fill alarms fire late. One function, DFUsedPercent, now serves
GetDiskUsage, readDiskUsage, the recovery-unit headroom projection and the deploy page's free percent. Tests use
numbers measured on demo-hp 9201 (/mnt/sys_drive: old 21.5 %, df 23 %); a source scan refuses a percent divided by
the whole filesystem (red-proved by putting the old line back). The label measured the docker data volume, not /.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/i18n/locales/en.json

@@ -630,7 +630,7 @@
   "common.magyar_felulet": "Hungarian interface",
   "common.megsem": "Cancel",
   "common.pi_kompatibilis": "Runs on Pi",
-  "common.rendszer_gyoker": "System (/)",
+  "common.rendszer_gyoker": "System",
   "common.torles": "Delete",
   "common.ugyfel_azonosito": "Customer ID",
   "common.ujrainditas": "Restart",